1. Field of the Invention
The present invention generally relates to the field of mobile telephony and particularly to a wireless communication network. More particularly, the present invention relates to a highly reliable wireless communication station receiver front-end for use in a wireless communication network, for example a 3rd Generation (3G) wireless communication network.
2. Description of the Related Art
In a wireless communication network, geographic areas are subdivided into a plurality of cells. The traffic in each cell is handled by a transceiver station for transmitting and/or receiving radio signals (voice and/or data) to/from mobile terminals. Such transceiver stations can be equipped with receiver front-ends whose main function is to select and amplify the radio signals that are received by an antenna connected to the receiver and are within the frequency range useful for communication and to attenuate all other potentially interfering signals.
A receiver front-end can be connected to two antennas, a primary antenna and a diversity antenna. The primary antenna is associated with both a primary receive path and a transmit path, while the diversity antenna is coupled to a diversity receive path, which includes a conventional bandpass filter and a low-noise amplifier. After the primary antenna, the primary receive path includes a conventional bandpass filter disposed within a conventional duplexer and an additional low-noise amplifier. The conventional duplexer further includes a conventional transmit filter coupled to the primary antenna as part of the transmit path.
Typically, communication from the mobile terminal to the transceiver station is characterized by radio signals having rather low power. Such radio signals are therefore subject to degradation in the presence of noise.
As disclosed in U.S. Pat. No. 6,263,215, in order to increase significantly the signal-to-noise ratio and hence the sensitivity of transceiver stations in receiving the radio signals transmitted by the mobile terminals, the stations can be equipped with cryogenic receiver front-ends.
In WO 02/21708 is for example disclosed a wireless base station cryogenic unit configuration including a diversity antenna and a main receiver. Main receiver receives and transmits signals simultaneously, wherein diversity receiver only receives signals. The corresponding signals are transmitted directly to a cryogenic unit in the case of the diversity antenna and to a diplexer for the main receiver before being forwarded to the cryogenic unit.
The diplexer is comprised of filters for separating the signal into a transmission signal component and a received signal component. The received signal component is then transmitted to the cryogenic unit. The cryogenic unit is comprised of HTS filters with amplifiers. Generally, amplifiers are low-noise amplifiers (LNA). The received signal is then forwarded to the amplifiers and in the case of the main receiver electrical pathway, diplexed with the transmission component of the signal by a further diplexer and then it is transmitted to the remaining sections of the base station.
The Applicant has observed that the above described receiver front-end has a relatively low reliability due to the fact that HTS filters and consequently the receiver front-end, become non-operative if the cryogenic unit does not work properly, for example due to refrigerator problems.
The Applicant faced the problem of realizing a receiver front-end having good performances and improved reliability.